1,254 research outputs found
Time-resolved photoluminescence of the size-controlled ZnO nanorods
Size dependence of the time-resolved photoluminescence (TRPL) has been investigated for the ZnO nanorods fabricated by catalyst-free metalorganic chemical vapor deposition. The nanorods have a diameter of 35 nm and lengths in the range of 150 nm to 1.1 mum. The TRPL decay rate decreases monotonically as the length of the nanorods increases in the range of 150 to 600 nm. Decrease of the radiative decay rate of the exciton-polariton has been invoked to account for the results. (C) 2003 American Institute of Physics.X11100sciescopu
Electroproduction of nucleon resonances
The unitary isobar model MAID has been extended and used for a partial wave
analysis of pion photo- and electroproduction in the resonance region W < 2
GeV. Older data from the world data base and more recent experimental results
from Mainz, Bates, Bonn and JLab for Q^2 up to 4.0 (GeV/c)^2 have been analyzed
and the Q^2 dependence of the helicity amplitudes have been extracted for a
series of four star resonances. We compare single-Q^2 analyses with a
superglobal fit in a new parametrization of Maid2003 together with predictions
of the hypercentral constituent quark model. As a result we find that the
helicity amplitudes and transition form factors of constituent quark models
should be compared with the analysis of bare resonances, where the pion cloud
contributions have been subtracted.Comment: 6 pages Latex including 5 figures, Invited talk at ICTP 4th
International Conference on Perspectives in Hadronic Physics, Trieste, Italy,
12-16 May 200
Differential cross sections and spin density matrix elements for the reaction gamma p -> p omega
High-statistics differential cross sections and spin density matrix elements
for the reaction gamma p -> p omega have been measured using the CLAS at
Jefferson Lab for center-of-mass (CM) energies from threshold up to 2.84 GeV.
Results are reported in 112 10-MeV wide CM energy bins, each subdivided into
cos(theta_CM) bins of width 0.1. These are the most precise and extensive omega
photoproduction measurements to date. A number of prominent structures are
clearly present in the data. Many of these have not previously been observed
due to limited statistics in earlier measurements
The Structure of the NPC1L1 N-Terminal Domain in a Closed Conformation
NPC1L1 is the molecular target of the cholesterol lowering drug Ezetimibe and mediates the intestinal absorption of cholesterol. Inhibition or deletion of NPC1L1 reduces intestinal cholesterol absorption, resulting in reduction of plasma cholesterol levels.Here we present the 2.8 Å crystal structure of the N-terminal domain (NTD) of NPC1L1 in the absence of cholesterol. The structure, combined with biochemical data, reveals the mechanism of cholesterol selectivity of NPC1L1. Comparison to the cholesterol free and bound structures of NPC1(NTD) reveals that NPC1L1(NTD) is in a closed conformation and the sterol binding pocket is occluded from solvent.The structure of NPC1L1(NTD) reveals a degree of flexibility surrounding the entrance to the sterol binding pocket, suggesting a gating mechanism that relies on multiple movements around the entrance to the sterol binding pocket
photoproduction on the proton for photon energies from 0.725 to 2.875 GeV
Differential cross sections for the reaction have been
measured with the CEBAF Large Acceptance Spectrometer (CLAS) and a tagged
photon beam with energies from 0.725 to 2.875 GeV. Where available, the results
obtained here compare well with previously published results for the reaction.
Agreement with the SAID and MAID analyses is found below 1 GeV. The present set
of cross sections has been incorporated into the SAID database, and exploratory
fits have been made up to 2.7 GeV. Resonance couplings have been extracted and
compared to previous determinations. With the addition of these cross sections
to the world data set, significant changes have occurred in the high-energy
behavior of the SAID cross-section predictions and amplitudes.Comment: 18 pages, 10 figure
Production of phi mesons at mid-rapidity in sqrt(s_NN) = 200 GeV Au+Au collisions at RHIC
We present the first results of meson production in the K^+K^- decay channel
from Au+Au collisions at sqrt(s_NN) = 200 GeV as measured at mid-rapidity by
the PHENIX detector at RHIC. Precision resonance centroid and width values are
extracted as a function of collision centrality. No significant variation from
the PDG accepted values is observed. The transverse mass spectra are fitted
with a linear exponential function for which the derived inverse slope
parameter is seen to be constant as a function of centrality. These data are
also fitted by a hydrodynamic model with the result that the freeze-out
temperature and the expansion velocity values are consistent with the values
previously derived from fitting single hadron inclusive data. As a function of
transverse momentum the collisions scaled peripheral.to.central yield ratio RCP
for the is comparable to that of pions rather than that of protons. This result
lends support to theoretical models which distinguish between baryons and
mesons instead of particle mass for explaining the anomalous proton yield.Comment: 326 authors, 24 pages text, 23 figures, 6 tables, RevTeX 4. To be
submitted to Physical Review C as a regular article. Plain text data tables
for the points plotted in figures for this and previous PHENIX publications
are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htm
Operative blood loss and use of blood products after full robotic and conventional low anterior resection with total mesorectal excision for treatment of rectal cancer
To date, no studies have investigated the estimated blood loss (EBL) after full robotic low anterior resection (R-LAR) in a case-matched model, comparing it with the conventional open approach (O-LAR). Forty-nine patients in the R-LAR and 105 in the O-LAR group were matched for age, gender, BMI (body mass index), ASA (American Society of Anesthesiology) class, tumor–node–metastasis (TNM) classification and UICC (Union for International Cancer Control) stage, distance of the lower edge of the tumor from the anal verge, presence of comorbidities, and preoperative hemoglobin (Hb). EBL was significantly higher in the O-LAR group (P < 0.001); twelve units of packed red blood cells were globally transfused in the O-LAR group, compared to one unit only in the R-LAR (P = 0.051). A significantly higher postoperative Hb drop (3.0 vs. 2.4 g/dL, P = 0.015) was registered in the O-LAR patients. The length of hospital stay was much lower for the R-LAR group (8.4 vs. 12.4 days, P < 0.001). The number of harvested lymph nodes (17.4 vs. 13.5, P = 0.006) and extent of distal margin (2.9 vs. 1.9 cm, P < 0.001) were significantly higher in the R-LAR group. Open surgery was confirmed as the sole variable significantly associated (P < 0.001) with blood loss (odds ratio = 4.41, 95% CI 2.06–9.43). It was a confirmed prognosticator of blood loss (P = 0.006) when a preoperative clinical predictive model was built, using multivariate analysis (odds ratio = 3.95, 95% CI 1.47–10.6). In conclusion, R-LAR produced less operative blood loss and less drop in postoperative hemoglobin when compared to O-LAR. Other clinically relevant outcomes were similar or superior to O-LAR
Oncoprotein HCCR-1 expression in breast cancer is well correlated with known breast cancer prognostic factors including the HER2 overexpression, p53 mutation, and ER/PR status
<p>Abstract</p> <p>Background</p> <p>Oncoprotein HCCR-1 functions as a negative regulator of the p53 and contributes breast tumorigenesis. The serum HCCR-1 assay is useful in diagnosing breast cancer and mice transgenic for HCCR developed breast cancers. But it is unknown how <it>HCCR-1 </it>contributes to human breast tumorigenesis.</p> <p>Methods</p> <p>Oncogene HCCR-1 expression levels were determined in normal breast tissues, breast cancer tissues and cancer cell lines. We examined whether HCCR-1 protein expression in breast cancer is related to different biological characteristics, including ER, PR, p53 genotype, and HER2 status in 104 primary breast cancer tissues using immunohistochemical analyses.</p> <p>Results</p> <p>HCCR-1 was upregulated in breast cancer cells and tissues compared with normal breast tissues. In this study, overexpression of HCCR-1 was well correlated with known breast cancer prognostic markers including the presence of steroid receptors (ER and PR), p53 mutation and high HER2 overexpression. HCCR-1 was not detected in the ER-negative, PR-negative, p53 negative and low HER2 breast cancer tissues. These data indicate that the level of HCCR-1 in breast cancer tissues is relatively well correlated with known breast cancer factors, including the HER2 overexpression, p53 mutation, and ER/PR status.</p> <p>Conclusion</p> <p>Determination of HCCR-1 levels as options for HER2 testing is promising although it needs further evaluation.</p
Search for the pentaquark in the reaction
A search for the \thp in the reaction was completed
using the CLAS detector at Jefferson Lab. A study of the same reaction,
published earlier, reported the observation of a narrow \thp resonance. The
present experiment, with more than 30 times the integrated luminosity of our
earlier measurement, does not show any evidence for a narrow pentaquark
resonance. The angle-integrated upper limit on \thp production in the mass
range of 1.52 to 1.56 GeV/c for the reaction is
0.3 nb (95% CL). This upper limit depends on assumptions made for the mass and
angular distribution of \thp production. Using \lamstar production as an
empirical measure of rescattering in the deuteron, the cross section upper
limit for the elementary reaction is estimated to be
a factor of 10 higher, {\it i.e.}, nb (95% CL).Comment: 5 figures, submitted to PRL, revised for referee comment
Photodisintegration of He into p+t
The two-body photodisintegration of He into a proton and a triton has
been studied using the CEBAF Large-Acceptance Spectrometer (CLAS) at Jefferson
Laboratory. Real photons produced with the Hall-B bremsstrahlung-tagging system
in the energy range from 0.35 to 1.55 GeV were incident on a liquid He
target. This is the first measurement of the photodisintegration of He
above 0.4 GeV. The differential cross sections for the He
reaction have been measured as a function of photon-beam energy and
proton-scattering angle, and are compared with the latest model calculations by
J.-M. Laget. At 0.6-1.2 GeV, our data are in good agreement only with the
calculations that include three-body mechanisms, thus confirming their
importance. These results reinforce the conclusion of our previous study of the
three-body breakup of He that demonstrated the great importance of
three-body mechanisms in the energy region 0.5-0.8 GeV .Comment: 13 pages submitted in one tgz file containing 2 tex file and 22
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